Box2D 对特定物体的重力？

发布于 2024-12-12 02:41:30 字数 487 浏览 0 评论 0原文

我看到每个人都说在 Box2D 世界中像这样添加重力：

b2Vec2 gravity = b2Vec2(0.0f, -10.0f);
bool doSleep = false;
world = new b2World(gravity, doSleep);

问题是，如果我只想在包含来自 CCSprite 的 userData 的特定 b2Body 上施加重力怎么办？ AFAIK 这会将重力应用于世界上我不想要的所有东西，所以有人可以向我解释一下如何将这种重力仅应用于特定的 b2Body 吗？

谢谢！

编辑1： 我可以只做这一行，

_bottomBody->ApplyForce(gravity, _bottomBody->GetPosition());

而不是世界=新的b2World...等等...难道这不是只在b2Body上使用重力吗？

原文

I see everyone saying that you add gravity like so in a Box2D world:

b2Vec2 gravity = b2Vec2(0.0f, -10.0f);
bool doSleep = false;
world = new b2World(gravity, doSleep);

The thing is though, what if I want gravity only on a specific b2Body which contains userData from a CCSprite? AFAIK this will apply gravity to everything in the world which I do not want, so can someone explain to me how I can apply this gravity only to a specific b2Body?

Thanks!

Edit1:
Can I just do this line,

_bottomBody->ApplyForce(gravity, _bottomBody->GetPosition());

Instead of the world = new b2World... etc... Wouldn't that work with gravity only on that b2Body?

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花想c 2024-12-19 02:41:30

只需每帧对特定的 b2Body 施加力/脉冲即可。它将模拟重力。

// a procedure called every frame
void Application::on_update_world(double t)
{
  m_body_with_custom_gravity->applyForce(CUSTOM_GRAVITY * m_body_with_custom_gravity->getMass());

  m_phys_world->Step(t, VEL_ITERATIONS, POS_ITERATIONS);
}

一个主题与您密切相关的问题：
如何在 Box2D 主体上施加恒定力？

Just apply a force/impulse to the specific b2Body every frame. It will emulate gravity.

// a procedure called every frame
void Application::on_update_world(double t)
{
  m_body_with_custom_gravity->applyForce(CUSTOM_GRAVITY * m_body_with_custom_gravity->getMass());

  m_phys_world->Step(t, VEL_ITERATIONS, POS_ITERATIONS);
}

A thread with a question closely related to your:
How to apply constant force on a Box2D body?

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